package com.warm.base.algorithm.structure.linkedlist;


import com.warm.base.algorithm.structure.array.Queue;

/**
 * @Date: 2019/12/2 16:06
 * @Author: LChuang
 * @Description:
 */
public class LinkedQueue<E> implements Queue<E> {

    private Node head, tail;
    private int size;

    public LinkedQueue(){
        head = null;
        tail = null;
        size = 0;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    @Override
    public void enqueue(E e) {
        if(tail == null){
            tail = new Node(e);
            head = tail;
        }else {
            tail.next = new Node(e);
            tail = tail.next;
        }
        size++;
    }

    @Override
    public E dequeue() {
        if(isEmpty()){
           throw new IllegalArgumentException("cannot dequeue from an empty queue");
        }
        Node retNode = head;
        head = head.next;
        retNode.next = null;
        if(head == null){
            tail = null;
        }
        size--;
        return (E) retNode.e;
    }

    @Override
    public E getFront() {
        if(isEmpty()){
            throw new IllegalArgumentException("queue is empty");
        }
        return (E) head.e;
    }

    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        res.append("Queue: front ");

        Node cur = head;
        while(cur != null) {
            res.append(cur + "->");
            cur = cur.next;
        }
        res.append("NULL tail");
        return res.toString();
    }
}
